418 
P ALTEON fOLOGY OF NEW YORK. 
This species may be distinguished from N. bucinum by its smaller size, more 
closely coiled volutions, and more regular surface-markings, especially in the 
even and closely arranged revolving strife. It differs from N. cornulum in its 
more elliptical transverse section, larger apical angle, and by its surface char¬ 
acters. This is the smallest form observed among the species of this genus 
in the Hamilton group, and it is of rare occurrence in the collections. 
Formation and localities. In the coarser, arenaceous shales of the Hamilton 
group, near Cazenovia, Madison county, N. Y. 
Nautilus maximus. 
PLATES LX1II, LXIV, AND SUPPLEMENT, 
Cyrtoceras maximum, Conrad. Geolo«\ Surv. of N. Y. : Pal. Dept., First Ann. Rep., p. 117. 1838. 
Nautilus maximus (Conr.), Hall. Illustrations of Devonian Fossils : Cephalopoda, pi. 64, fig. 1; pi. 64 A, 
fig. 1. 1876. 
Shell very large, subdiscoid, gibbous, becoming very ventricose. Volutions 
about three, contiguous, not re-entrant. Umbilicus wide and deep, exposing 
all the volutions. Transverse section subcircular, flattened on the concave 
dorsal side. Tube regularly and gradually enlarging to a point near the 
aperture. Apical angle about 14°. 
Chamber of habitation very large and ventricose, occupying half a volution 
or more. In the larger individuals it is free from the inner volution for 
about one-third of its length. Length of the grand chamber more than 
twice its greatest diameter, gradually contracting toward the aperture from 
a point about two-thirds of its entire length from the base. Aperture 
slightly oblique to the axis of the tube, opening upward. Air-chambers 
numerous, regular and very deep, gradually increasing from the apex, and 
measuring on the convex side, sometimes more than thirty mm.; the last 
one shallower than several of those preceding. 
Septa regular, distant, very concave, the concavity greater than the depth 
of the air-chambers; strongly imbricating. The distance between the septa 
is variable in different specimens, but in the same individual is nearly con¬ 
stant, with a gradually increasing distance. Measurements taken from the 
convex side of the outer volution of three individuals show four chambers in 
